1. Field of the Invention
The present invention relates generally to heat exchangers for automobiles, and more particularly to a seal structure for joint portions between tanks and tubes for the passage of a heat exchanging medium, and a method of making the seal structure.
2. Description of the Prior Art
Heat exchangers of the type described include, for example as disclosed in Japanese Utility Model Laid-open Publication No. 58-158985, two confronting tanks connected together by a plurality of parallel spaced tubes each having a multiplicity of radial fins. A heat exchange medium led into one of the tanks through an inlet formed therein is circulated through the tubes via the other tank and then discharged from an outlet formed in the one tank. During circulation, the heat exchange medium is subjected to heat-exchange with air passing around the fins so that air is heated by taking up heat from the heat exchange medium.
The tanks are formed of a synthetic resin material and each composed of an end plate and a tank case joined together at their confronting peripheral edge portions, as shown in Japanese Patent Laid-open Publication No. 55-312045.
The tubes are generally made of metal such as a copper alloy and joined at their opposite ends to the end plates of the respective tanks in such a manner as shown here in FIG. 5 of the accompanying drawings.
As shown in FIG. 5, the end plate 6 has a plurality of tube reception holes 9 in which respective one ends of the tubes 2 are fitted with tubular seal lips 11d of rubber seal gasket 11 disposed between the tubes 2 and the end plate 6 and then they are sealingly assembled with the end plate 6 by radially expanding the ends of the tubes 2.
Prior to this assembling operation, the sealing gasket 11 is placed on the end plate 6. However, since the seal gasket 11 made of rubber is flexible, it is difficult to fit the tubular sealing lips 11d of the sealing gasket 11 simultaneously into corresponding ones of the tube reception holes 9. Further, the sealing lips 11d are likely to be bent inwardly or folded by the tubes 2 when the tubes 2 are inserted into the tube reception holes 9, as shown in FIG. 6. The seal lips 11d thus folded may cause a sealing failure such as leakage of the heat exchange medium.